The role of events as information for properties of objects and layout is the theoretical question underlying this research, as well as previous research of the principal investigator's. This research aims to investigate development of perception of the affordance of a surface of support and detection of varied information for such a surface in reaching (5 mo), crawling (9 mo), and walking (12 m0) infants. Experiments in Part I will investigate exploratory and locomotor behavior in relation to properties of a surface per se (rigidity and deformability). In Part II, supplementary information in the form of impact events will be added to an otherwise ambiguous surface in a real layout. Exploratory and locomotor behavior will be monitored. A second experiment will use films of the impact events and surfaces of variable rigiddity in a habituation-recovery paradigm. The question is whether prelocomotor infants can detect surface properties through impact information, and whether discrimination measured by habituation predicts appropriate crawling behavior in a real layout where perception of an affordance can be monitored. In Part III, experiments with impacts on a surface, and collisions of objects will investigate whether infants can use information from varied kinetic events to detect underlying invariant information for substance. The study as a whole throws light on development of the ability to differentiate the substance of objects and surfaces and to detect whether surfaces are safe for locomotion.